Turn a screen diagonal into the width and height that decide whether it fits.
The number the display is sold by — 27", 34", 55".
16:9 for most monitors and TVs, 21:9 or 32:9 for ultrawides, 16:10 for many laptops, 4:3 for older panels.
23.5 × 13.2 in
A 27-inch 16:9 panel measures 23.5 by 13.2 inches of active area — 59.8 cm by 33.6 cm. Add bezel and a stand before comparing that against the space you have.
What this cannot tell you
Take this with you
Screen Dimensions from Diagonal on RunTheTests — free browser-based device tools, no sign-up.